Beekeeper Wu Chao-sheng recalled his shock when he went to tend to his bees on an unusually cold April day in 2007.

“I opened the hive, but only saw about two-thirds of the bees remaining,” the 50-year-old said. “My father and I thought they died from overwork.”

Wu, who has run the family business for about 30 years and is the president of the Taiwan Beekeepers Association, said he was not even among the hardest hit, with other bee farmers seeing their annual honey production decline by half that year.

Like Wu, many Taiwanese beekeepers remain haunted by the events of 2007, when millions of bees were reported to have mysteriously “disappeared” across the country.

Those worries were rekindled recently by reports of the rapidly diminishing bee population in the US.

According to a recent New York Times article, the US saw nearly half of its bee hives wiped out last year because of colony collapse disorder, with neonicotinoids — a type of pesticide that is also commonly used in Taiwan — named as the main culprit.

On Monday, the European Commission said it would impose a ban on three pesticides that are harmful to bees starting on Dec. 1.

On the surface, Taiwan’s bee population appears to be more stable than that in the US, but local scientists are worried about the potential threat to agriculture and the ecosystem from what lurks unseen — the lack of systematic data, scientific research and general knowledge about bees in the country.

They said the government has not paid enough attention to the insects’ plight and has been reluctant to study how the widespread use of pesticides has affected bee populations.

“The government does not care at all about the life and death of bees,” said Yang En-cheng (楊恩誠), an entomology professor at National Taiwan University.

At stake is the more than NT$50 billion (US$1.7 billion) in produce pollinated by bees — from melons, longans, apples and oranges to cruciferous vegetables like cabbage.

Yang believes that bees in Taiwan are starting to come under pressure from pesticides — specifically neonicotinoid overuse — but government officials contend that there is no direct evidence supporting the contention, citing statistics that show an increase in bee numbers.

According to the Council of Agriculture’s latest statistical yearbook, the number of bee hives in the nation has been on the rise since 2007, and increased 6 percent in 2011 to 103,870.

Honey production also soared 85 percent in 2011 to 15,089 tonnes, which Tsai Lung-tsung, the council’s point man on bees, said suggests that most of these natural pollinators are in good condition.

Scientists dismiss the figures as unreliable, or at least not reflective of the damage neonicotinoids are doing to local bees’ nervous systems, which Yang said he has observed in his research.

Chen Yu-wen (陳裕文), dean of the Department of Biotechnology and Animal Science at Yilan University, said that unlike in the US, where bees have died suddenly, the pesticide was affecting bees in Taiwan in a way that might actually be masking the problem.

“The bees seem drunk,” Chen said. “They don’t necessarily die from the pesticides, but certainly cannot navigate under their influence,” making them worthless as pollinators.

Chen was unable to provide an estimate of how many of the nation’s bees are punch-drunk because of the lack of data, but he is doing research, which he expects to complete in August, to try to pinpoint bee numbers and the environmental factors to which they are exposed.